This invention relates to a device for reading an information carrier on which an information pattern is recorded in the form of substantially parallel running tracks of readable effects or features, the device comprising a read head for generating a read signal by scanning the information carrier at a scanning position, servo tracking means for keeping the scanning position on the track, and discriminating means for determining the type of information carrier, the information pattern having at least one different physical parameter for each type of information carrier.
Such a device is disclosed in U.S. Pat. No. 4,724,492. This device is suitable for playing an audio Compact Disc (CD), a video Laser Disc with an FM-modulated audio signal (LD) and a video Laser Disc with a digital audio signal (LDD). During playback, the recorded information signal is recovered from the information pattern, while the signal processing and the settings of the servo means, among which drive motor control and servo tracking means, are to be adapted to the respective type of information carrier. For this purpose, the device includes discriminating means for determining a type of information carrier. The CD is distinguished on the basis of the diameter which is sensed by a sensor. The LD and LDD differ in recorded information pattern in the presence of the digital audio signal. To distinguish the LD from the LDD, the servo means are set, the disc is brought to speed and the read head is positioned over the track by the servo tracking means. Then, part of the information pattern is scanned during which operation the read signal is demodulated for recovering the information signal. A discrimination circuit finally detects the presence of the digital audio signal in that the frame sync occurs in the information signal.
A problem in the prior-art device is that for discriminating the types of information carriers in which only the information pattern is different, a complicated procedure is to be applied, which leads to the time-consuming determination of the type of information carrier.